In a conventional thin film transistor liquid crystal display (TFT-LCD), since a liquid crystal panel of the TFT-LCD itself does not emit light, displaying can be performed by means of an external light source. Generally, the external light source includes a backlight-type light source and a reflective-type light source. Since the backlight-type light source is unnecessarily affected by environmental changes, the light sources of the current TFT-LCDs are almost backlight-type light sources.
In the TFT-LCDs, the light sources have experienced two types, i.e., from CCFL (cold cathode fluorescent lighting) to LED (light emitting diode). At present, the LED has become a main light source of the TFT-LCD because of its advantages of small volume, rapid time response, long service life, unbreakable, high color gamut, a variety of capsules and so on.
Currently, a LED backlight module basically includes an edge-type LED backlight module and a direct-type LED backlight module. The edge-type LED backlight module has merits of low power consumption and thin thickness, but since it has to use a light guide plate, it is heavy and its cost is high. The direct-type LED backlight module uses a small number of light sources without using a light guide plate, thus, its cost is low; but its light box is relatively high, thus, it looks thicker in appearance.
Quantum Dot (QD) phosphor is a phosphor that may achieve the highest color saturation among current phosphors, because its color purity is extremely high due to a relatively narrow FWHM (Full Width at Half Maximum) of its luminescent spectrum (i.e., merely 20 to 40 nm). However, since the QD phosphor is synthesized using chemical solutions, it is difficult to be uniformly dispersed in silicone, and it is afraid of water and oxygen and has serious thermal quenching in luminescence. Thus, if the QD phosphor is directly encapsulated in the LED, the LED will be caused to have low brightness and bad endurance, and it is difficult to achieve batch production at present.
At present, all methods of achieving batch production of the QD phosphor adopt remote phosphor solutions, one of which is to adopt a sandwich structure, that is, the QD phosphor is encapsulated in an optical film, and then it is used in cooperation with other optical films; and the other one is to encapsulate the QD phosphor in a glass tube to form a QD tube, wherein the QD is placed in the front of the LED and fixed using a support device when it is used.
However, currently, the optical film encapsulated with the QD phosphor cannot be made oversized (e.g., larger than 100 inches) due to a limitation of a cabinet, thus, the oversized application is limited. The QD tube may be merely used in the edge-type backlight module, and it is easily breakable, thereby having a low reliability.
Thus, in a current oversized LCD, since the size is large, a transmittance of a liquid crystal panel is low, the brightness is required to be high (i.e., at least 1000 nits), and a color gamut is demanded to be high (i.e., more than 92%), it is difficult to apply the QD technique to the oversized LCD by adopting current conventional design means.